TW200417300A - A process and an apparatus for coating printed circuit boards with laser-structurable, thermally curable solder stop lacquers and electroresists - Google Patents

Abstract

A process and an apparatus for coating printed circuit boards with a laser-structurable, thermally curable solder stop lacquer and electroresists are described.

Description

200417300 (1) 发明. Description of the invention [Technical field to which the invention belongs] The present invention relates to a method and a device for coating a printed circuit board with a laser-structured, heat-hardening paint and an antistatic agent. [Prior art] Printed circuit boards are all coated with solder resist paint, especially with photosensitive paint, so that the conductor can be protected, and only the holes left and the area to be soldered are free of solder. Although screen printing was not available until 1975, since then, the sensitivity of photosensitive solder resist lacquers in this field has become more and more complex, and only through Confirmation of photochemical method. These paints are preferably applied via a screen casting method. This is described in European patent application EP 0 002 040 A1. This coating technique raises several issues. These are all particularly related to the reduced viscosity of the edge regions of highly delicate conductors having a width / height of 100 / zm, especially during drying, when the paint applied with a viscosity of 500 mP as flows down the edges of the conductors. This problem can be solved by making the material highly thixotropic and volatile solvents. The printed circuit board was initially dried at a low temperature on a chain-bucket lifter to dry the lacquer onto the conductor. Secondly, hot air drying is performed. The problem of coating high conductors is also specifically solved by spray coating. According to all these coating methods, drilled holes are also coated. The varnish flowing within it after being electro-structured is also dissolved out. The soldering method of this solder resist is affected. Electrical structure on one side! 〇 In the cover. Because L 1200 is used to add air in the coated room. However, the light dissolving in the tank and -4- (2) (2) 200417300 non-developed welding zone caused great pollution of wastewater. The quality of the lacquer is particularly damaged by the alkaline development path, as these must provide the corresponding carboxyl groups that destroy affinity and humidity. The acrylate required for the photovoltaic structuring method affects the softening range of the solder resist paint, which is particularly disadvantageous during soldering with lead-free solder materials at high soldering temperatures. Because of the further development of miniaturization, this generation of solder resist paint faces new problems. Thus, in particular, the uncertainty of development has an adverse effect. All these problems can be solved by using laser structured solder resist. Therefore, through the C02 laser, the welding area and the remaining ring of the drilled hole are not painted. A developing method is not required. Thus, no polymerization waste occurs. The laser can be positioned very correctly. Problems such as film offset do not occur. The use of non-photosensitive, heat-curable solder masks has currently failed because there are no coating methods available to achieve paint-free drilling. European patent application EP 0 766 90 8 describes a roll coating method, coating the opposite side with a photopolymerizable coating agent to make a multi-chip module, wherein the metering roll can be heated to 25 to 6 (TC and The dressing roller can be cooled to 5 to 20 ° C. The heating of the lacquer causes evaporation and drying of the lacquer layer that has not been transferred to the rubber surface of the dressing roller. The cooling causes condensation. The coating of the edge area of the conductor at the height of the conductor is When 50 // m and the thickness of the paint layer is 50 // m, a thickness of 13 // ni can be achieved. The drilling cannot fail without lacquer. The coating viscosity is as high as 20,000 to 100,000 mPas. To 200 // m coating thickness. For the application of solder resist, the coating rate between 5 and 20 m per minute is too high because good coating of the edge area cannot be achieved. (3) (3) 200417300 This high coating rate is also described in German patent application DE 101 31 027 A1 (Name: Method and device for high-speed coating of wood / plastic and metal surfaces). Therefore, it can be hardened by irradiation. The powder coating is preferably supplied from a storage container for powder via a melting roller It is not practical to use heat-curable lacquer only, because the hardening reaction and sintering effect occur in this case. In order to coat the bottom side, a melting roller is immersed in a storage container for unmetered powder For coating. In the case of thermosetting lacquers, this results in the hardening of the stored material. The same situation also exists in European patent application EP 0 698 233 B1, which describes the application of radiation-hardened coatings from molten materials. There is no known method to achieve the purpose of the invention. It is exclusively related to a lacquer system that can be hardened by irradiation. Nor can it achieve the absence of lacquer on the edge area necessary for the transportation of printed circuit boards. It can be used Solder masks contain mineral fillers to increase viscosity, especially to prevent the paint from overflowing the side walls of the conductor. These mineral fillers are usually contained in the solder mask in a weight fraction from 20 to 50 wt .-%. If these are available, The welding paint is structured by a laser, and the ash residue will remain on the welding area and form a mushroom-like pattern. This hinders clean welding and makes it more difficult. Also, it is not guaranteed that the drilled holes are not painted. [Summary of the invention] The purpose of the present invention is to solve the aforementioned problems that occur in the coated printed circuit board of the conventional technology. A main object of the present invention is to provide a better solution. Heat-curable solder resist varnish and anti-electric agent, as well as providing a lightning-free method for the formation of residues-6- (4) (4) 200417300 Radio-structured method and device, and in the case of thin and high conductors, low thickness The lacquer layer, the clean, closed lacquer surface covers the edge area well, and at the same time, the edges and drilled holes of the printed circuit board are well covered. The subject of the present invention is a coating with a solder resist paint or an antistatic agent. Circuit board device comprising at least one light-weight roller coating device having an upper rubber-coated guide roller, a lower rubber-coated coating roller, and a coating gap with the coating roller for solder resist paint or anti-electric agent A storage container is arranged above the roll coating device, a mechanism for conveying the printed circuit board, a mechanism for drying the solder resist paint, and a device for turning the printed circuit board. The roll coating device has only A coating unit for coating the bottom side of the printed circuit board. The preferred embodiments of the device according to the present invention are all the subject matter of claims 2 to 6. The present invention further relates to a method for coating a printed circuit board with a solder resist paint or an antistatic agent, comprising the following steps: (i) supplying the printed circuit board to a coating having only one bottom side for coating the printed circuit board Roll coating device for coating units, (ii) metering solder resist or anti-electric agent with viscosity of 4000 to 15000 mPas at 25 ° C, or metering powder coating, (quickly) coating the varnish on the bottom of the printed circuit board On the side, (iv) at a temperature sufficient to reduce the viscosity of the lacquer to less than 300 mP as or to reduce the viscosity of powder coating to less than 500 mPas, dry the coated printed circuit board for a period of time to harden the lacquer and Make it non-sticky, and (v) flip the printed circuit board, and perform steps (i) to (iv) in the same roll coating device or in a device of -7- (5) (5) 200417300 . The preferred embodiments of the method according to the present invention are the subject matter of claims 8 to 10 in the scope of patent application. Finally, the present invention relates to a solder resist paint and an antistatic agent that can be structured by laser, having a solid content of 50 to 100 wt .-% and a viscosity of 5000 to 15000 mPas at 25 ° C. The preferred embodiments of this solder resist paint or anti-electrostatic agent are the main points of items 13 to 17 of the scope of patent application. [Embodiment] The present invention will be explained in more detail below. The application of the lacquer can be performed using a conventional technique, as long as the coating device used has only one coating unit to coat the bottom side of the substrate. In the case of using, for example, a device according to item 1 of the scope of patent application, a solder resist lacquer having a viscosity of preferably 5000 to 15000 mpas at 25 ° C and a solid content of 50 to 100% can be hardened and cured. Thermally hardened, and preferably containing no or only a small amount of mineral aggregate, the lacquer is supplied to the first roll coating device (2) 'and a printed circuit board provided with a drilled hole of conductor and mating conductor components ( 1) The roll coating device (2) includes an upper rubber-coated guide roller (3), a lower rubber-coated dressing roller (4), and a metering roller (5) that forms a metering gap with the coating roller (4). A wedge-shaped coating knife (8) can be optionally arranged between the dressing roller (4) and the metering light (5) so that the edge area of the printed circuit board is not painted. A high-viscosity solder resist paint is counted from the storage container (6) arranged above the roll coating device (2) ^ 8-(6) (6) 200417300 The amount is measured between the metering roller (5) and the dressing roller (4) between. A solder resist having a viscosity of preferably 5000 to 15,000 mPas is preferably a smoothness at a rate of 1 to 4 m / min and preferably a smoothness of 10 to 70 // m (Rz = 5 // m The thickness of the layer above 10 // m) and the soft (20 to 40 Shore A) rubber surface is applied to the bottom side of the printed circuit board (1). In the case of this highly viscous coating, only a part of the paint layer on the applicator roll is transferred due to the high adhesive strength of the paint on the rubber coating. The need for paint transfer is based on the strength of the adhesion on the surface of the printed circuit to be coated. Because this adhesive strength shows the highest 値 in the copper conductor (10), the thickest lacquer layer is applied here. None of the drilled holes could form an adhesion area, and no paint was transferred there. According to the conventional roller coating method, the lacquer is applied by a grooved rubber coating method, so that the lacquer is pressed out of the groove, and the lacquer is also pressed into the borehole. In the method according to the invention, the coating takes place independently of the nature of the surface to be coated. Therefore, the applied solder resist varnish covers the conductor excellently and keeps the edge areas of the drilled holes and the printed circuit board free of varnish. Therefore, a good solder wire assembly is ensured and the printed circuit board is transported into the dryer. By the highly viscous coating according to the present invention, the rubber surface can be prevented from being damaged by cutting by a high conductor. After this coating, the printed circuit board (1) is transported into a dryer such as an infrared dryer via a mechanism (7) for transporting the printed circuit board such as a chain transport mechanism with a transport clip. Below a transport path with, for example, an IR-irradiator (1 1). These are equipped with irradiators in the medium wavelength range (2 to 4 #m). -9- (7) (7) 200417300, which is the opposite of the evaporation path used in the combustion chamber of the chain bucket elevator, in the evaporation path, the lacquer is dried without reducing the viscosity, so that it will not be reduced due to viscosity The edge area of the overflow conductor, the method according to the invention aims at the opposite effect. The viscosity of the lacquer should be reduced as quickly as possible, from an initial value of 5,000 to 15 00 mP as to less than 500 mP as. Therefore, the paint flows onto the side walls of the conductor before the wavy paint surface is smoothed. The absence of mineral aggregates can facilitate this flow method. The temperature of the lacquer should rise to 100 to 120 ° C within 10 to 60 seconds. It can be prevented from falling through the beginning of drying and the corresponding increase in viscosity. The borehole and edge areas remain unpainted. Secondly drying can cause hardening of the paint. After the non-sticky and hardened non-adhesive and printed circuit board (1) is flipped in a turning mechanism (1 3), if it is not coated a second time with the same device, it is supplied to a second roller constructed in the same way Coating device. It can be seen from Fig. 3 that in the case of a paint layer thickness of 30 / m, the edge of the conductor (14) usually has a coating of 5 to 10 // m. Using the method according to the invention, as shown in Fig. 4, the coating of the edges of the conductor (14) can reach more than 10 // m. According to the present invention, the foregoing results can be achieved by blending a part of a non-volatile solvent having a melting point of more than 120 ° C in an amount of 5 to 20 wt .-%, and by not having a mineral filler. In the case of powdered solder resist, the aforementioned results are achieved by reducing the viscosity to less than 500 mPas. Without mineral filler, it can also prevent the formation of mushroom-shaped residual ash on the copper surface during laser structuring. According to a further embodiment, the device for carrying out the method according to the invention shows a further metering roller (9). Between the metering rollers (5) and (9), the high-viscosity solder resist quilt from the storage-10- (8) (8) 200417300 storage container (6) arranged above the roll coating device (2) Measurement. In the case of using a thermosetting powder solder resist paint, the paint is applied through a filter box (1 2) to a metering roller (5) which rotates in a relative direction compared with the dressing roller (4). The metering roller (5) absorbs the varnish maintained on the dressing roller (4), and the powder solder resist is then spread thereon. Therefore, the initial hardening can be avoided, and the roll dressing of the heat-hardening powder solder resist can be performed. After the thickness adjustment of the metering rollers (5) and (9), through the film adhered to the fixed metering roller (9) having a thickness of about 30 to 150 // m, it is possible to achieve no paint on the edges. . Partially, this paint is transferred to a smooth (Rz = 5 to 10 // m) and soft (20 to 40 Shore hardness A) dressing roller (4) via a metering roller (5) running in the opposite direction. On the surface of the rubber, and at a rate of 1 to 4 m / min and a layer thickness of 20 to 70 // m, a lacquer having a viscosity of preferably 5000 to 15000 mPas is applied to the bottom side of the printed circuit board (1). In the case of using a heat-hardening, powder solder resist for coating, each roller and the printed circuit board to be coated are heated to a temperature which can achieve the viscosity required for coating. _ The present invention will be explained in more detail with the following examples: Example 1: A 3 00 x 4 2 x 1.5 mm printed circuit board according to NEMA's FR4 type, with a maximum conductor height of 100 / ^ πm and a conductor width of 150 // m. Solder mask: Probimer 65 Fa. Vantico AG 1 00 parts by weight 5 parts by weight 7-butyrolacton -11-(9) (9) 200417300 Roller coating device: RC Fa. Biirkle , Rubber coated 100mm, 30 Shore hardness a, Rz5 // m gap width: 1 0 0 // mt silk dressing: 5 0 // m rate: 2 m / min infrared irradiator: the first irradiator has 2 // m wavelength, the second irradiator has a wavelength of circulating air temperature: 1 2 0 ° C dryer length: 4 m result · thickness of the drying film: 3 0 // m at a conductor height of 1 00 μm Edge area coating: 1 1 11 m drilling diameter 300 to 1000 / zm: without lacquer. Example 2: A 300 x420 x 1.5mm printed circuit board (2) based on NEMA FR4 type, with a maximum conductor height of 100 // m and a conductor width of 150 // m.

Solder mask (1) ·· 125 parts by weight + Riitapox VE 3746 80wt ·-% methylglycol, Fa. Bakelite AG 0.5

parts by weight 2-ethyl-4-methylimidazole, Fa · BASF Viscosity: at 25 ° C 9 5 00 mPas (10) (10) 200417300 at 1 6 0 TG after 1 hour hardening: 1 5 5 ° C Light weight coating device: RC Fa. Btirkle, rubber coating 100mm, 30 Shore hardness A, Rz5 // m Gap width: 1 00 // m wet Dressing: 5 〇 // m rate: 2 m / mi η infrared irradiator: the first irradiator has a wavelength of 2 / zm, the second irradiator has a wavelength of 4 # m circulating air temperature: 120 ° C dryer length : 4 m for 1 hour at 160 ° C. Coating result: Thickness of dry film: 30 // m Coating in the edge area in the case of a conductor with a height of 100 // Π1: 11 U m Drilling diameter: 300 to 100 μm: No lacquer structured via laser Result: Co2 Laser: Welding area does not have ash residue. Soldering result: The drilling and soldering areas are cleaned and wetted by solder. Example 3: 3 00 X 4 20 x 1.5mm printed circuit board according to NEMA FR4 type, conductor height is 100 / zm, conductor width (11) 200417300 solder mask: 8 0.0 parts by weight EPOSID VP 868-2, 70 wt .-% Duro-plast-Chemie 19.5 parts by weight HAT 9490 K reso 1 η ο vo 1 ak 100 wt .-% Fa. Vantico 0.5 parts by weight 2 -ethyl-4-methyl ethyl-4- __methylimidazole) Fa. BASF_

10 0 parts by weight 75 wt .-% Viscosity TG at 25 ° C 7500 mPas Hardened at 160 ° C for 1 hour TG: 150 ° C Roll coating device: RC Fa. Robert Btirkle GmbH Freudenstadt, rubber Coating 100mm, 30 Shore hardness A, Rz 5 // m Gap width: 1 2 0 // m Wet dressing: 5 0 // m Transfer quantity: 42 v. 1 .-% Φ rate: 2 m / mi η infrared irradiator: the first irradiator has a 2 # m wavelength, the second irradiator has a 4 // m wavelength circulating air temperature: 120 ° C dryer length: 4 m Coating result: Thickness of dry film: 3 0 // m Coating on the edge area when the conductor is 1 00 // m height: 1 1 -14- (12) 200417300 μ m drilling diameter is 3 00 to 1 000 // m: edge area of printed circuit board without lacquer: 5 mm without lacquer structured by laser Result: C02 laser: welding area without ash residue Combustion gas: halogen-free soldering result: diamond The holes and solder joints are cleaned wet by the solder.

Example 4: A 300 x 420 x 1.5 mm printed circuit board based on NEMA's FR4 type, with a maximum conductor height of 100 // m and a conductor width of 100 // m. Solder mask: 8 0.0 parts by weight EPOSID VP 868-2, 70 wt .-% Duro-plast-Chemie

19.5 parts by weight HAT 9490 Kresolno volak 100 wt .-% Fa. Vantico 0.5 parts by weight 2 -ethyl-4-methylimide

_methylimidazole) Fa · BASF 10 0 parts by weight 75 wt .-% Viscosity: 7 25 00 mPas at 25 ° C Roll coating device: RC Fa. Robert Biirkle GmbH Freudenstadt, rubber coating thickness 100mm, 30 Xiao Hardness A, Rz 5 // m Gap width between metering rollers (5) and (9): 1 20 // m -15- (13) 200417300 Wet dressing: 5 0 // m Transfer quantity: 4 2 ν ο 1.-% Teflon film on the metering roller (9), the opening area at the right edge: 4 1 0 mm speed: 2 m / min infrared irradiator: the first irradiator has 2 // m wavelength, the second irradiator has 4 // m wavelength circulating air temperature: 1 2 0 ° C φ dryer length: 4 m Example 5: 3 00 x 4 2 0 x 1.5 mm according to FR4 type of NEMA The maximum height of the printed circuit board conductor is 100 // m, and the conductor width is 100 // m. Powder solder mask:

95.00 parts by weight epoxy DER 671 Fa. Dow Chemical 4.5. Parts by weight dicyandiamide 0.5 parts by weight 2-methylimidazole (2 -_ methylimidazole) Fa. BASF__

100.0 parts by weight Powder solder mask Melting range: 65 -7 8 ° C

Viscosity: 14.00 mPas at 1 10 ° C Particle size: 10-20 // m TG after hardening at 160 ° C for 1 hour TG: 16 (TC • 16- (14) (14) 200417300 Roll coating device: H RC Fa. Robert Biirkle GmbH Freudenstadt, rubber coated 10mm, 30 Shore A, Rz5 // m

The temperature of the dressing roller (4) and the measuring rollers (5) and (9): 110 ° C The temperature of the printed circuit board: 1 10 ° C The Teflon film on the measuring roller (9) is on the right edge Opening area: 410 mm Gap width between metering rollers (5) and (9): 5 0 // m Dry dressing: 3 0 // m _ Number of transfers: 60 vol .-% Speed: 3 m / min Infrared irradiator: the first irradiator has a wavelength of 2 // m and the second irradiator has a wavelength of 4 // m. circulating air temperature: 140 ° C dryer length: 4 m result · first coating: Lu Thickness of dry film: 3 0 // m Edge area coating in the case of a conductor with a height of 1 00 // m: 11 β m Drilling diameter of 3 00 to 1 000 // m: No varnished printed circuit board Edge: 5mm without lacquer result. · Second coating: Thickness of dry film: 3 0 // m -17- (15) (15) 200417300 Apply at the edge area when the conductor is 100 // m height. Cover: 12 fi m drilling diameter 300 to 1000 // m: no lacquered edge of printed circuit board: 5 mm without lacquer structured by laser Result: C02 laser: welding area without ash residue combustion gas : Halogen welded result: drilling and welding solder wetted area cleanly. φ [Brief description of the drawings] Fig. 1 schematically shows the device of the present invention. Figure 2 shows a further embodiment according to the invention for use in powder coating. FIG. 3 schematically shows a printed circuit board coated by a conventional technique. Figure 4 shows a printed circuit board coated by the method according to the invention. Comparison table of main components 1 Printed circuit board 2 Roller coating device 3 Rubber-coated guide roller 4 Rubber-coated dressing roller 5 Metering roller 6 Storage container 7 Mechanism for conveying printed circuit board-18- (16) 200417300 8 Coating knife 9 Metering roller 10 Copper conductors 11 Transport resistance 12 Screen box 13 Turning machine 14 Coating of the structural edge area of the conductor edge welding paint

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Claims (1)

200417300 Π) Pick up and apply for patent scope 1 · A device for coating a printed circuit board (1) with solder resist paint or anti-electric agent includes at least one rubber-coated guide roller (3) and rubber-coated dressing on the lower part The roller (4), the light-weight (5) roll coating device (2) that forms a metering gap with the dressing roll (4), and a storage container (6) for solder resist paint or anti-electric agent is arranged in Above the roll coating device (2), a mechanism for conveying the printed circuit board (7), a mechanism (1 1) for drying the solder resist paint, and a device for turning the printed circuit board, the roll coating The device (2) has only one coating unit for coating the bottom side of the printed circuit board. 2. The coating device according to item 1 of the scope of patent application, wherein the dressing roller (4) has a hardness of 20 to 40 Shore hardness A and a roughness Rz of 5 to 10 // m. A coating device according to item 1, wherein the device further comprises a wedge-type coating knife between the application roller (4) and the metering roller (5). _ 4. The coating device according to item 1 of the patent application scope, wherein the device further comprises a second metering roller (9) forming a metering gap with the first metering roller (5), and the first metering roller (5) A storage container (6) or a sieve box in the case of powder coating is placed on top. 5. The coating device according to item 1 of the patent application range, wherein the metering rollers (5, 9) are all heatable. 6. The coating device according to item 4 of the patent application range, wherein the metering rollers (5, 9) are all heatable. -20- (2) (2) 200417300 7. The coating device according to any one of claims 4 to 6, wherein the second metering roller (9) is a fixed metering coated with a plastic film In this way, by stripping the film, the required coating area can be freed. 8 · —A method of coating a printed circuit board (1) with solder resist or an antistatic agent, comprising the following steps: (i) supplying the printed circuit board (1) to only one bottom side for coating the substrate The roll coating device of the coating unit of (1) measures the solder resist paint or anti-electric agent with a viscosity of 4000 to 15,000 mPas at 25 ° C, or measures powder coating, (iii) applies the lacquer to the printing On the bottom side of the circuit board (1), (iv) dry the coated printed circuit board (1) at a temperature sufficient to reduce the viscosity of the paint to less than 300 mPas or to reduce the viscosity of powder coating to less than 500 mPas. ) The lacquer is hardened and made non-sticky for a period of time, and (v) the printed circuit board is turned over, and steps (i) to (iv) are performed in the same roll coating apparatus or in a further such apparatus. 9. The coating method according to item 8 of the patent application, wherein step (iv) is performed at a temperature of 100 to 12 (TC for a period of 10 seconds to 1 minute. 1). Coating method, wherein the lacquer is rolled at a roll speed of 0.2 to 4 m / s, preferably 0.5 to 4 m / s, and most preferably 1 to 4 m / s, 10 to 1 0 0 // m 1 1. The coating method according to item 8 of the patent application scope, which has a solid content of 50 (3) (3) 200417300 to 100 wt .-% and a solid content of 5000 to 15,000 mPas. Viscosity paint or antistatic agent is used as solder resist or antistatic agent. 1 2. A laser structured solder resist and antistatic agent, in which the solder resist or antistatic agent has 50 to l The solid content of 〇〇wt .-% and the viscosity of 5,000 to 15,000 mPas. 1 3. For example, the solder mask and anti-electric agent in the scope of the patent application No. 12, which is essentially free of materials. 14. If the solder resist paint and anti-electric agent of item 12 of the patent application scope, which can be heat hardened or hardened by irradiation. 1 5. If the solder resist paint and anti-electrode agent of item 13 of the patent application scope, Where it can be heat hardened or irradiated Hardening. 16. The solder resist paint and anti-electric agent according to any one of the claims 11 to 15 in the scope of patent application, which are halogen-free. 1 7 · The solder resist paint in the scope of patent application No. 12 And anti-electric agent, in which the paint has a solvent content of boiling point above 120 ° C of 50 to 20 wt .-%. 18. The solder resist paint and anti-electric agent such as item 12 of the patent application scope, wherein It contains halogen-free epoxy resin. 1 9 · If the solder resist paint and anti-electric agent of item 12 of the patent application range, the solder resist paint can be heat hardened, and the powder solder resist has a temperature of 80-1 20 ° C. Viscosity at a temperature of 1 0000- 1 5000 mPas. 20 · —A kind of printed circuit board can be obtained by using the method according to any one of the patent application scopes 8 to 11. -22-